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Permeability Converter

Science

Convert intrinsic permeability between darcy, millidarcy, square metres, and square centimetres — used for petroleum engineering and porous media.

Reviewed by the thecalcu.com team · Last updated July 3, 2026

From
To
All conversionsfor 1 Millidarcy (mD)
Square Metres (m²)9.8692e-16
Square Centimetres (cm²)9.8692e-12
Darcy (D)0.001
Millidarcy (mD)1
Square Feet (ft²)1.0623e-14

What is a Permeability?

The Permeability Converter converts intrinsic permeability between darcy and millidarcy (the standard petroleum industry units), square metres and square centimetres (SI/metric), and square feet (imperial). Intrinsic permeability measures how easily a fluid flows through a porous material's structure, independent of the fluid's own properties, a foundational quantity in petroleum reservoir engineering and groundwater hydrology.

Enter a value in any supported unit and the converter calculates the equivalent instantly.

Why Use a Permeability Converter?

Petroleum reservoir data is almost universally reported in millidarcy, a scale chosen specifically because it produces convenient numbers for typical reservoir rock, while scientific and engineering calculations sometimes require the SI-consistent square-metre unit. Converting between these, spanning many orders of magnitude, requires careful attention to the exact scientific notation involved.

Who Should Use This Converter?

  • Petroleum and reservoir engineers converting core sample permeability data between darcy units and SI units for reservoir simulation.
  • Groundwater hydrologists working with aquifer permeability data across different unit conventions.
  • Geotechnical engineers converting soil or rock permeability specifications for foundation or containment design.
  • Materials scientists working with porous media (filters, membranes) permeability data.

What Insights Does the Permeability Converter Give You?

The main output is the converted value in your chosen target unit, calculated precisely from the fixed multiplier relationship between units. Because permeability spans an enormous range across materials, from highly permeable gravel to nearly impermeable clay, the converter helps confirm a value is realistic for the type of material involved.

How to use this Permeability calculator

  1. Choose your starting unit from the source dropdown, for example, "Millidarcy (mD)".
  2. Enter the numeric value you want to convert in the input field.
  3. Choose your target unit from the destination dropdown, for example, "Square Metres (m²)".
  4. Read the converted result, which updates instantly as you type or change units.
  5. Use the swap (⇅) button if you need to reverse the conversion direction.
  6. Use the copy button to grab the result for a reservoir engineering calculation or hydrology report.
Show formula & methodology ↓Show less ↑

Formula & Methodology

The converter's base unit is square metres (m²). Every supported unit has a fixed multiplier:

- 1 square centimetre (cm²) = 0.0001 m²
- 1 darcy (D) ≈ 9.869233 × 10⁻¹³ m²
- 1 millidarcy (mD) ≈ 9.869233 × 10⁻¹⁶ m²
- 1 square foot (ft²) = 0.092903 m²

Any conversion follows:

Result = Input × (toBase of source unit ÷ toBase of target unit)

Worked example, converting 100 millidarcy (typical conventional reservoir rock) to m²:

Result = 100 × 9.869233 × 10⁻¹⁶ = 9.869 × 10⁻¹⁴ m²

This confirms the very small SI-unit value corresponding to a moderately permeable reservoir rock sample.

Related Tools

You may also find these useful: Flow Converter, Density Converter, Kinematic Viscosity Converter.

Frequently Asked Questions

What is intrinsic permeability?
Intrinsic permeability measures how easily a fluid can flow through a porous material (like rock or soil), depending only on the material's pore structure, not on the fluid's properties like viscosity. It's a key parameter in petroleum reservoir engineering and groundwater hydrology.
What is a darcy, and why is it used instead of m²?
A darcy is a practical unit of permeability defined so that typical reservoir rock permeabilities fall in a convenient range (roughly 1 to 1,000 millidarcy for many oil and gas reservoirs), whereas the SI unit (m²) would produce extremely small, unwieldy numbers, 1 darcy equals approximately 9.869 × 10⁻¹³ m².
How do I convert millidarcy to darcy?
Divide the millidarcy value by 1,000, since one darcy equals 1,000 millidarcy. Enter your value with 'Millidarcy (mD)' as the source and 'Darcy (D)' as the target to apply this automatically.
What is a typical permeability value for oil and gas reservoir rock?
Conventional oil and gas reservoirs commonly have permeabilities ranging from about 1 to 1,000 millidarcy, while unconventional 'tight' formations can have permeabilities well under 1 millidarcy, requiring specialised extraction techniques like hydraulic fracturing to produce economically.
How is intrinsic permeability different from hydraulic conductivity?
Intrinsic permeability depends only on the porous medium's structure, while hydraulic conductivity (used in groundwater hydrology) also incorporates the specific fluid's properties (density and viscosity), the two are related but conceptually distinct, with hydraulic conductivity being more directly useful for water flow calculations specifically.
Why is permeability measured in units of area (m², cm²)?
Permeability's SI unit works out to area (m²) because of how it's defined in Darcy's law relating flow rate, viscosity, pressure gradient, and cross-sectional area, this area-based unit is mathematically correct even though permeability isn't literally describing a physical area.
How is permeability measured in a laboratory?
Core samples from a reservoir or aquifer are typically tested in a permeameter, which measures fluid flow rate through the sample under a controlled pressure gradient, then calculates permeability using Darcy's law from the measured flow, pressure, viscosity, and sample geometry.
Why does permeability matter for groundwater and aquifer studies?
Aquifer permeability determines how quickly groundwater can flow and be extracted, directly affecting well yield predictions, contaminant transport modelling, and sustainable groundwater management decisions.
Can permeability values span a very wide range?
Yes, permeability varies enormously across materials, from highly permeable gravel and clean sand (thousands of darcy) to nearly impermeable clay and unfractured shale (microdarcy or lower), spanning many orders of magnitude depending on pore structure and connectivity.
What industries commonly need permeability unit conversion?
Petroleum and reservoir engineering, groundwater hydrology, geotechnical engineering, and materials science (for filters and porous media design) all routinely work with permeability data, often needing conversion between the petroleum industry's darcy units and SI-based scientific units.
Also known as
permeability converterdarcy to millidarcy converterpetroleum permeability unitsporous media permeability converterintrinsic permeability converter